- Joined
- Feb 13, 2001
- Location
- Twin Cities
Thought some of you might find this interesting. My new Abit NF7-S motherboard arrived about an hour ago. Having read that it does not read the CPU on-die therma, diode, I set about looking into whether that diode could be read using an external reader chip like the MAX6657 or AD1023 via the SMBus. The Winbond W83627HF chip on the board has three inputs that can be configured for either a 10k thermistor or thermal diode junction. The motherboard uses the first two along with the on-board thermistors to read the bottom of the CPU temperature and the system temperature. That left the third one unused. In previous AMD motherboards, all you needed to do was run a shielded two conductor cable from CPU socket pins S7 and U7 to a reader chip, assuming those two pins did not already connect to some other circuitry. Upon investigating those pins, my ohmeter said they went to some circuitry. Closer investigstion revealed that there is a small IC under the thermistor in the CPU socket well. It is an ATTANSIC ATTP1. That is a device with two inputs, one being from an on-die thermal diode and the other from the thermistor inside the CPU socket well. Its purpose is to monitor the temperature represented by either input and when a resistor programmed threshold is crossed, it shuts down the power supply. The response time is 1us. That's good news for owners worried about frying their CPU if the heatsink fails, but not such good news if you wanted to use the on-die thermal diode pins for driving an external reader.
If I get the urge, some day I will figure out how to isolate the conductor from the on-die Thermal diode going to the ATTP1 and route it out to either an external reader or the unused input on the Winbond chip. PDF files are available from the manufactures for both chips and in the case of the Winbond, a recommended circuit shows how to implement an on-die Thermal diode.
Hoot
If I get the urge, some day I will figure out how to isolate the conductor from the on-die Thermal diode going to the ATTP1 and route it out to either an external reader or the unused input on the Winbond chip. PDF files are available from the manufactures for both chips and in the case of the Winbond, a recommended circuit shows how to implement an on-die Thermal diode.
Hoot